Process for reclaiming ammonium and zinc values from sal-ammoniacflux skimmings.



J. MOPETRJBGB. PROCESS FOR REGLAIMING AMMONIUM AN D ZINC VALUES PROM SL-AMMONIAG FLUX SKIMMINGS. APPLICATION FILED 1111011 1909. 1 %,55T/m Patented Nov 19, 9.12.

, mg, oxychlorids.

, eltimmings in the form of tine granules. On

. in a liquid form the soluble zinc and ainnicit tlilh ldlltlhl,

JUSEFH IEECFETRIDGE, 8F VANI'ERGRIFT, FENNtEYLV'ANIA, ASSIGNOR T0 AMERICAN SHEET :5; TIN PLATE COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION 015 NEW JERSEY.

PROCESS! FOE; REGLAIMING iLIVIMQNIUIII AND ZINC VALUES FRQM SAL-AlVEMONIAG- FLUX SKIMIVIILIGS.

Specification of Letters Patent. Application filed December 11, 1909.

latented'h ov. 19, 19312.

Serial No. 532,654,

To all whom it may concern..-

Be it knoivn that Joeurrr ll'lCFE'li'ilDGE, Vandergrift, Vl estmoreland county, Pennsylvania, have invented a new and use; ful Process for lteclaiming Ammonium and Zinc Values from Sal Ammoni ac Flux Skimmings, of which the following a full, clear, and exact description, reference being had to the accmnpanying drawings, forming part of this specificatii'm, in \vhichfirst of these methods the .yolatile zinc and I I I i I I I Figure l is an elevation partly in section, I I

ammonium chloride arc los and in the second method, the insoluble zinc salts are of value only as zinc ore.

According to prior methods of removing the soluble salts by weathering or subjecting to steam, the soluble salts on the surface of each lump or particle are dissolved, leaving a lightiilm or protective coating of oxid of zinc on the surface of each lump. This light film of oxid retarded action so that the mass could be disintegrated and the soluble portions dissolved out only after long contact.

The objectof my invention is to recover, by a rapid and convenient process, from these shimmings the iui'mioniuni and zinc values contained therein. The QlTlll'lOnlllDl values are recovered in the form of a hydrate, sulfate or chlorid. The soluble zinc salts are recovered as carbonate of :aincfand the insoluble zinc salts are recovered as zinc oxid and. metallic zinc.

The features of my invention which most prominently distinguish it from the prior and largely diagrammatic, of apparatus which may be employed in carrying out my invention; and Fig. 2 is a detail sectional view of a portion of one of the filters which may he employed.

My invention has relation to a novel method of reclain'iing ammonia and zinc values from salammoniac flux skimmings. The skimmings are a by-product obtained when I sal-ammoniac is used as a flux in galvanizing steel or iron, the bath of molten. zinc be ing protected from the action of the air by sal-ainmoniac. They consist of a mixture of zinc oxid, zinc chlorid, zinc oxychlorid, metallic zinc and chlorid of ammonium, with small quantities of ferrous chlorid, oxid of iron, tin and lead. The proportions of the various ingredients depend very largely on the exact nature of the shop practice Where f which the rock-like mass of salainmoniac skimmings is disintegrated, the soluble salts separated from the insoluble, and the soluble zinc salts converted into zinc carbonate of such purity as to be available for the drug trade or for line pigments. Also the recovery of the ammonium as commercial hydrate, sulfate, or chlorid 0t an'nnonium; also the conversion of the insoluble oxid and 0XV- the skimmings are produce When eal-aminoniac is used as a flux or protective coating for a zinc bath, the fluxis replenished from time to time by the additicn of fresh sal-ammoniac. This cal-ammoniac is continually decomposing, forming chlorid of zinc into oxid of zinc suitable flu zinc chlorid, which dissolves the oxid of use a commercial pigment, while the mczinc from the surface of the zinc bath, form- When the flux becomes highly charged with ehlo'rid, oxid and oxychlorid of zinc, it is skimmed oil by means oit 'perforated ladies or Skimmers, more or metallic zinc being removed With the tallie zinc is reclaimed such and can be used for galvanizing iron or steel.

I will now describe in detail the proton-oil method of carrying out my invention. In accordance therewith, the sail ammoniac skunmings are first broken into a convenient size for handling, and are digested with water in a suitable mill, preferably a ball mill, such as indicated all 2 in Fig. 1, being maintained at a temperature of from preterably 160 to 180 degrees Fahrenheit by ad mitting live steam through the hollow shaft oi the mill. The water at once dissolves I the soluble salts I cooling, the sliirnmings solidify into a herd rock-like mass. Heretofore a portion of the nine has been recovered from these skimmings by Well known pyro methods of extracting zines from ores; also by steaming the slzininiings for several days, recovering on the surface of the mass, and by rotating theniill, the friction the the grinding balls on the charge of selenium salts smelting the insoluble residue to recover values therel'trcin.

methods known to me, are the rapidity with niac skimmings removes the light film of.

oxid of zinc to thereby constantly expose fresh surfaces for the action of the hot Water. In from one to two hours the charge is disintegrated,the soluble salts being in solution, the fine insoluble oxids and oxychlorids being held in suspension, and the metallic zinc free from zinc salts being in granular form. The charge is then removed from the digester 2 through a suitable opening at, and is admitted into a wooden tank 5, which is provided with rotary agitating arms 6 and a drag chain 7. The charge is kept in a state of gentle agitation in this tank by the rotating arms 6, the fine insoluble oxid and oxychlorids of zinc being held in suspension, while the granules of metallic zinc drop to the bottom and are freed from adhering 7; The soluble o-xids by the drag chain chlorids and suspended oxids and oxychlorids are drawn off through a pipe 8 to a centrifugal pump 9. The metallic zinc is removed from the tank 5 through the gate 10 and is returned to the galvanizing department, or is melted and cast into slabs of commercial zinc.

From the pump 9, the liquor is forced into the filter press 11, which may be of any suitable character, and thesoluble zinc and ammonium chlorid contained therein are separated from the insoluble zinc oxid and oxychlorid. The mixture of oxid and oxychlorid of zinc is mixed with caustic lime in quantities equivalent to thechlorin contained in the oxychlorid, and are furnaced at a dull red in a mutlie furnace. The oxychlorid of zinc is decomposed by the lime and heat, forming chlorid of calcium and oxid of Zinc. The oxid of zinc formed by the decomposition of the oxychlorid of zinc, together with the oxid of zinc originally present, are separated from the chlorid of calcium by digest-ing with water in a suitable agitating tank, and then filtering, both being reclaimed as oxid of zinc, which may be used as pigment.

The zinc and ammonium chlorid liquor separated from the oxid and oxychlorid of zinc by the filtering press 11, flows through a pipe 12 into an oxidizing agitator 13. In this agitator the small percentage of ferrous chlorid present. is converted into ferric chlorid by treating with a'suitable oxidizing agent, preferably chlor'in. Nhen the iron has been converted to the higher chlorid, it is precipitated in the agitator 13 by adding oxid of zinc, or by carbonate of zinc formed by adding carbonate of soda in such quantities that from one-half to one per cent. of zinc chlorid is decomposed to form carbon ate of zinc, which, like the oxid of zinc, has the property of precipitating iron in the form of pcroxid from solutions of zinc chlorid when the iron is in the form of ferric chlorid. The precipitated iron is removed from the liquor by passing it through a suitable filter l5. The clear liquor from the filter 15 flows by gravity through a pipe 16 into a precipitating tank 17. The liquor is heated in this tank to near its boiling point by means of live steam admitted through pipe 18. The liquor is kept in a state of gentle agitation by suitable rotating stirring arms 10, and a hot carbonate of soda solution is added until all the zinc is precipitated as carbonate. The liquor with the suspended carbonate of zinc is drawn off through pipe 20 into a suitable filter 21, where the zinc carbonate is separated. This carbonate of zinc may be dried and sold as such, or it may be converted into zinc oxid by furnacing in a suitable muffle furnace to expel the carbonic acid.

The liquor from the filter 21 may be elevated by a centrifugal pump 22 into an iron still 23, and there treated with milk of lime to decompose the ammonium salts and liberate free ammonia. This free ammonia is expelled by live steam admitted through a pipe 24, and is carried through pipe 25 into 'an absorption tower 26, where it is absorbed in water, sulfuric acid or hydrochloric acid to form either a hydrate, sulfate or chlorid of ammonium.

It will thus be seen that my invention pro vides a simple and effective process of a continuous nature, whereby all the zinc and ammonium value contained in the sal-ammw niac skimmings may be recovered in available form.

I do not intend to limit myself to the exact mode of treatment which I have herein shown and described, as the same may be modified somewhat in detail by those skilled in the art; nor do I limit myself to the use of the particular apparatus which I have indicated in the drawings, since various forms of apparatus capable of carrying out the process are well known to chemists and others skilled in this art.

What I claim is 1. In the art of reclaiming ammonium and Zinc values from sal-ammoniac flux skimmings, the method which consists in digesting the flux skimmings with water and steam while grinding the same by attrition to disintegrate the skimmings, separating the insoluble oxids and oxychlorid of zinc from metallic zinc and soluble zinc and ammonium salts" by agitation, settling and filtration, mixing the zinc oxid and oxychlorid with lime in quantities equivalent to the chlorin contained in the oxychlorid, furnacing the mixture to decompose the oxychlorid of zinc and form oxid of zinc and chlorid of calcium, then dissolving the chlorid of calcium by digesting with warm water, and filtering to remove chlorid of calcium and to recover the zinc as oxid of zinc; substantially as described.

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